Hello. After talking with Serebii himself, I've decided to write more lengthier summaries as opposed to bullet point style. You can find accompanying pictures linked here, but to maintain flow of everything, it'd just be one giant block summary.
https://twitter.com/taddlelegacy/status/1108422818113306625
Soliera asks if that’s a Pokemon, but Zossie says that in the past it combined into a four-legged Pokemon and asks Moon for confirmation. Moon explains that it’s called the Zygarde Cell while Rotomdex explains that individually, they can’t attack. Stakataka loses balance and is defeated by Lunala. Sun explains to Soliera that even if Zygarde can’t attack, it can cover the eyes by sticking on it. The rest was simply just leaving it up to Moon and Lunala. Soliera is surprised that Sun was able to figure this out on his first encounter with it, but Zossie says that they’re the incarnations of the moon and it’s because they’re a group that you can trust and rely on each other.
At this moment, the auras that surround Lunala, Sun, and Moon strengthens and becomes visible. At the top of the tower is Dusk Mane Necrozma, still visibly weakened and in pain even after augmenting Solgaleo into its body. It notices the aura emanating from Lunala and jumps off the tower to encounter it, ejecting Solgaleo out of its body.
Back at the Poni Altar, Commander Phyco meets up with Lusamine, who disappointingly tells her that she won’t be able to use Lunala to get across to the Ultra Megalopolis. He says he ran late because he was trying to cooperate with Naganadel. Lusamine asks if it’s also an Ultra Beasts and Phyco responds saying that it is and it’s a UB that treats them nicely. Lusamine calls it beautiful as it creates a purring noise. Phyco warns her about the three needles that protrude out of its body, saying that it’s venomous. Lusamine then asks if it’s a Poison-type, but Phyco has no idea what that means.
Lusamine then attacks the Naganadel in a battle with her own Pokemon, severely beating it down and then captures it with her Beast Ball. She then holds the Beast Ball up to her chest saying that the capture was a success and the Ultra Beast is now *her* Pokemon. Phyco then is confused at the Beast Ball because now they’ve lost their way back to the Ultra Megalopolis. But Lusamine explains to him that it’s not a problem, all the Beast Ball did was capture it and it’ll listen to her now. She then sends it out and gently pets it calling it her cute child as it also embraces her back. She then says that this is also needed for the salvation of the “Blinding One.”
Back to the Ultra Megalopolis, Necrozma approaches Sun and Moon injured. Soliera explains to them that it’s the Blinding One. Moon puts two and two together from what Anabel said back before the time skip about “The Blinding One.” She realizes that it’s “The Blinding One’s” power and this world’s science fault that caused them to lose their light. Soliera clarifies that it was formally known as Necrozma.
Soliera explains the backstory for Necrozma, that it used to not just roam around Ultra Megalopolis, but across all of Ultra Space illuminating the entire reaches of the worlds from corner to corner and the other side of the Ultra Space. She then explains that foolish humans tried to take control of this energy by controlling it, but in the process, a piece of its body broke off and went missing. Because of this, even though the wound was cured, it wasn’t actually whole and light kept cracking out of it and vanished. Necrozma would then try to regain light and become whole, but in the process, all light was lost. More backstory comes to light where Soliera reveals that her predecessors managed to contain Necrozma into this tower to provide artificial light. She then talks about why it went after the avatars of the Sun and Moon because travel from Ultra Megalopolis and Alola was made possible because of the Aether foundation. Necrozma was able to merge Solgaleo, but its light wasn’t enough.
Sun then realizes that Necrozma is going to go after Lunala as it did with Solgaleo, then he and Moon can’t go back to Alola. He commands Lunala to take out Necrozma before it takes it out. The battle starts with Lunala initiating with a Moongeist Beam, but Necrozma dodges out of the way and claws Lunala in the chest before it has time to fire another shot and slams it into the ground. Sun and Moon summon all their available Pokemon to pincer attack Necrozma as it’s focused on Lunala, but they’re all swept away from what appears to be a horde of Naganadels with Lusamine, Phyco, and Aether agents. Phyco introduces her as Lusamine and she declares that she and her foundation will be the ones to carry out the salvation for the Blinding Ones.
Upon hearing the Foundation’s name, Sun pauses and loses his temper and aks if she’s the one who told Faba to take his grandpa’s island. And not just that, but now she’s taking Lunala. Moon tries to calm Sun down, but he doesn’t give budge. Lusamine respond with “Take?” looking confused and concerned at Sun. Lusamine becomes more visibly and visibly upset, asking what did she take from him? If anything, it's her that got something taken away. If anything, it was she who couldn't do anything. So she vowed to become strong and beautiful. Tears fall from her eyes and she opens a Beast Ball containing a giant Nihilego. Three speech bubbles appear saying, “Come. Come, my child. Let's become one/join together.” Nihilego swallows her, much to Sun and Moon’s horror becoming Mother Beast.
That's all for this month's of CoroCoro Ichiban!